The invention relates to a punching tool for taking a biological sample from a filter using punching, the punching tool comprising a punch and a die provided with a punching channel for conveying the sample from the upper surface of the die to the lower end of the die. More precisely, the invention relates to a punching tool also provided with a guidance means of the sample that comprises a guidance channel arranged as an extension of the punching channel for receiving the sample from the punching channel, the diameter of the guidance channel is 1.02 to 2× the diameter of the punch and is greater than the diameter of the punching channel, and at the connecting point with the punching channel the guidance channel forms a shoulder and broadens towards the free end of the guidance means. In this context the diameter of the punch naturally refers to the diameter of the cutting end of the punch.
Publication DE 3942170 discloses such an instrument for taking paper samples in order to determine the basis weight (grammage) of paper.
A punching tool is known in the art for taking a biological sample that comprises a punch and a die provided with a punching channel for conveying the sample from the upper surface of the die towards the lower end of the die. Such an instrument can be used to take blood samples, saliva samples, tissue fluid samples and other body fluid samples. The filter is typically a planar sheet made of fibrous material such as paperboard, cardboard or paper, from which several samples with a small diameter can be taken. The diameter of the sample typically ranges from 0.8 to 3.2 mm. The shape of the samples is generally circular, and can therefore be referred to as discoidal. The sample is transferred from the instrument to a small vessel placed beneath it, when the sample has successfully been punched from the sheet. The vessel is a small cup that can easily be delivered to the laboratory where the sample will be analysed. There may be dozens of vessels adjacently attached to one another, thus forming a structure that resembles a square when seen from above.
A problem with the instrument intended to be used for taking a biological sample is that the sample is not necessarily always released from the instrument. This is due to the fact that the edges of the sample include fluff originating from the fibres in the filter that may adhere to the different parts of the instrument. When taking biological samples it is known to register the release of a sample, and therefore the punching can be repeated if required, meaning that another punching may be performed, if the punching tool has not registered the release of the sample and a successful punching. However, a new punching does not necessarily lead to the desired result, instead each hundredth sample remains adhered to the instrument, from where it may eventually with time be released and fall into an incorrect vessel. Such a mistake does not only decelerate sample taking but also causes the sample to be registered into an incorrect vessel, which may relate to an incorrect person or animal. It is obvious that such a mistake may have fatal consequences.
The punching tool should at times be disassembled and cleaned. The disassembling and cleaning should be carried out more frequently, the more mistakes occur during punching.